Peak/bottom detection circuit, A/D converter, and integrated circuit

ABSTRACT

A peak/bottom detection circuit is disclosed. A comparator compares a voltage of one of three or more capacitors with an input voltage. A calculation amplifier amplifies the voltage of one of the three or more capacitors. Each of three or more switches respectively corresponding to the three or more capacitors connects a corresponding capacitor among the three or more capacitors to one of the comparator, the calculation amplifier, and a source of the input voltage. A controller generates control signals for sequentially switching connection destinations of the three or more capacitors and to supply the control signals to the three or more switches, respectively, in which the connection destinations of three capacitors among the three or more capacitors are different from each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority of theprior Japanese Patent Application No. 2018-009781, filed on Jan. 24,2018, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The disclosures herein relate to a peak/bottom detection circuit, an A/Dconverter, and an integrated circuit.

2. Description of the Related Art

Conventionally, a technology has been known in which an Analog toDigital (A/D) converter is connected to a subsequent stage of a peakhold circuit including a comparator and a capacitor, and a peak value ofa voltage is acquired by converting a voltage output as an analog amountfrom the peak hold circuit into a digital value.

RELATED-ART DOCUMENTS Patent Document

[Patent Document 1] Japanese Laid-open Patent Publication No. H04-31771

[Patent Document 2] Japanese Laid-open Patent Publication No.2003-215173

SUMMARY OF THE INVENTION

According to an embodiment, a peak/bottom detection circuit, includingthree or more capacitors; a comparator configured to compare a voltageof one of the three or more capacitors with an input voltage; acalculation amplifier configured to amplify a voltage of one of thethree or more capacitors; three or more switches respectivelycorresponding to the three or more capacitors, each of the three or moreswitches configured to connect a corresponding capacitor among the threeor more capacitors to one of the comparator, the calculation amplifier,and a source of the input voltage; and a controller configured togenerate control signals for sequentially switching connectiondestinations of the three or more capacitors and to supply the controlsignals to the three or more switches, respectively, in which theconnection destinations of three capacitors among the three or morecapacitors are different from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating an Analog to Digital (A/D) converter ofa first embodiment;

FIG. 2A and FIG. 2B are diagrams for explaining switches of the firstembodiment

FIG. 3A and FIG. 3B are diagrams for explaining a switch between a peakdetection mode and a bottom detection mode;

FIG. 4 is a timing chart for explaining an operation of a peak/bottomdetection circuit in the peak detection mode;

FIG. 5 is a timing chart for explaining an operation of the peak/bottomdetection circuit in the bottom detection mode;

FIG. 6A and FIG. 6B are diagrams for explaining an example of acomparator;

FIG. 7 is a diagram illustrating an example of a calculation amplifier;

FIG. 8 is a diagram illustrating an A/D converter in a secondembodiment;

FIG. 9 is a first diagram illustrating an example of an integrateddevice of a third embodiment;

FIG. 10 is a second diagram illustrating the example of the integrateddevice of the third embodiment; and

FIG. 11 is a diagram illustrating an example of an arrangement ofpeak/bottom detection circuits in an integrated circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a conventional method described above, a dead time occurs where apeak hold circuit is not able to detect a peak of a voltage.Specifically, periods of a dead time correspond to a period for anAnalog to Digital (A/D) converter to sample outputs of the peak holdcircuit, and a settling period for bringing a voltage of a capacitor,which is reset when the sampling ends, close to a voltage of a detectiontarget.

In the following, embodiments of the invention will be described withreference to the accompanying drawings. The embodiments described belowenable control against occurrences of dead time.

First Embodiment

Referring to drawings, a first embodiment will be described below. FIG.1 is a diagram illustrating an Analog to Digital (A/D) converter of thefirst embodiment.

An A/D converter 100 of the first embodiment includes a peak/bottomdetection circuit 200, and an A/D conversion section 300. The A/Dconverter 100 outputs a value acquired by converting a voltage output asan analog signal from the peak/bottom detection circuit 200 into adigital value by the A/D conversion section 300.

The peak/bottom detection circuit 200 of the first embodiment includespower sources 201 and 202, current sources 203 and 204, a comparator205, a calculation amplifier 206, a controller 210, capacitors C1, C2,and C3, switches SW1, SW2, SW3, SW4, and SW5, which are collectivelycalled switches SWn (n=1, 2, 3, 4, and 5).

The power source 201 outputs a power voltage to be targeted (to be amonitor target) to detect a peak value and a bottom value by thepeak/bottom detection circuit 200. In the first embodiment, a voltage tobe targeted to detect the peak value or the bottom value by thepeak/bottom detection circuit 200 is regarded as, but not limited to,the power voltage output from the power source 201. The peak/bottomdetection circuit 200 detects the peak value or the bottom value of thevoltage input to a non-inverting input terminal of the comparator 205;however, this voltage may be that output from any device.

In the peak/bottom detection circuit 200, the non-inverting inputterminal of the comparator 205 is connected to the power source 201.Also, an inverting input terminal of the comparator 205 is connected tothe switches SW1, SW2, and SW3. Moreover, the inverting input terminalof the comparator 205 is connected to a connection point with the switchSW4 and the switch SW5. An output terminal of the comparator 205 isconnected to the controller 210. In other words, a CMPO signal, which isan output signal output from the comparator 205, is supplied to thecontroller 210.

For instance, the comparator 205 of the first embodiment is preferably acomparator having a response speed of 1 [nsec] or more. Moreover, forinstance, the comparator 205 of the first embodiment may be realized bycausing a clocked comparator to conduct a self-excited operation.

The switch SW4 is connected between the current source 203 coupled tothe power source 202 and the switch SW5. The switch SW5 is connectedbetween the switch SW4 and the current source 204 coupled to a ground.

The current source 203 charges and discharges the capacitors C1 to C3through the switch SW4 in a peak detection mode, which will be describedlater. Moreover, the current source 204 charges and discharges thecapacitors C1 to C3 through the switch SW5. A speed of a charge and adischarge by the current sources 203 and 204 may be approximately 100[mV/nSec].

In the calculation amplifier 206, one input terminal is connected to theswitches SW1, SW2, and SW3, and another input terminal inputs an outputsignal of an output terminal of the calculation amplifier 206, so as toform a voltage follower circuit. The output terminal of the calculationamplifier 206 is connected to an input terminal of the A/D conversionsection 300, and a DETO signal, which is an output signal of thecalculation amplifier 206, is supplied to the A/D conversion section300.

For instance, the calculation amplifier 206 of the first embodiment ispreferably an operational amplifier responding at approximately 100[mV/μSec]. Moreover, the calculation amplifier 206 of the firstembodiment amplifies a voltage value of a capacitor Cn at a hold stagedescribed later, and outputs the amplified voltage to the A/D conversionsection 300 of a subsequent stage.

The capacitor C1 is connected between the switch SW1 and the ground, thecapacitor C2 is connected between the switch SW2 and the ground, and thecapacitor C3 is connected between the switch SW3 and the ground.

Each of the switches SW1, SW2, and SW3 includes a terminal P, a terminalD, a terminal H, and a terminal C. Terminals C of the switches SW1, SW2,and SW3 are connected to corresponding capacitors C1, C2, and C3,respectively.

Moreover, in each of the switches SW1, SW2, and SW3, the terminal P isconnected to the power source 201, the terminal D is connected to theinverting input terminal of the comparator 205, and the terminal H isconnected to the one input terminal of the calculation amplifier 206.

Each of the switches SW1, SW2, and SW3 of the first embodiment connectsthe terminal C to any one of the terminal P, the terminal D, and theterminal H in response to control signals SWn_P, SWn_D, and SWn_H (n=1,2, or 3) supplied from the controller 210.

In other words, the switches SW1, SW2, and SW3 connect the capacitor C1,C2, and C3, respectively, to one of the power source 201, the comparator205, and the calculation amplifier 206, in response to the controlsignals SWn_P, SWn_D, and SWn_H supplied from the controller 210.

At this time, the controller 210 generates, for each of the switchesSW1, SW2, and SW3, the control signals SWn_P, SWn_D, and SWn_H so as toconnect the terminal C to a different connection destination.

For instance, the controller 210 controls the switch SW2 to connect theterminal C to the terminal D and controls the switch SW3 to connect theterminal C to the terminal H, in a case of connecting the terminal C tothe terminal P at the switch SW1. Moreover, the controller 210 connectsthe terminal C of the switch SW2 to the terminal P and connects theterminal C of the switch SW3 to the terminal H in a case of connectingthe terminal C to the terminal D at the switch SW1.

As described above, the controller 210 switches the connectiondestination of the terminal C in order so as to differentiate theconnection destinations of the terminals C, respectively, at theswitches SW1, SW2, and SW3. In other words, the controller 210 of thefirst embodiment subsequently switches the connection destinations ofthe capacitors C1, C2, and C3 by the switches SW1, SW2, and SW3.

At the switch SW4 of the first embodiment, ON and OFF (connection anddisconnection) are controlled by a control signal SWP supplied from thecontroller 210. At the switch SW5, ON and OFF (connection anddisconnection) are controlled by a control signal SWB supplied from thecontroller 210.

The CMPO signal, a STB (strobe) signal, and a MODE signal are input tothe controller 210 of the first embodiment. Moreover, the controller 210generates and outputs the control signals SWn_P, SWn_D, and SWn_H, andthe control signals SWP and SWB. Also, the controller 210 of the firstembodiment includes a mode switching section 220.

The mode switching section 220 of the first embodiment switches anoperation mode of the peak/bottom detection circuit 200 in response tothe MODE signal. The peak detection mode is a mode that detects the peakvalue of the power voltage of the power source 201, and a bottomdetection mode is a mode that detects the bottom value of the powervoltage of the power source 201. Moreover, the controller 210 of thefirst embodiment generates the control signal SWP and the control signalSWB in response to the MODE signal and the CMPO signal.

The CMPO signal is regarded as an output signal of the comparator 205.In other words, the CMPO signal is a signal that indicates a result fromcomparing the voltage supplied from the power source 201 with a voltageof any one of the capacitors C1 to C3 connected to the comparator 205.

The STB (strobe) signal is regarded as a timing signal to read data.More specifically, the STB signal corresponds to a timing signal to readthe voltage of the capacitor Cn connected to the calculation amplifier206. For instance, the STB signal may be input from a high-level deviceor the like of the peak/bottom detection circuit 200.

The MODE signal is a signal that sets an operation mode of thepeak/bottom detection circuit 200 to the peak detection mode or thebottom detection mode. The MODE signal may be input from the ahigh-level device or the like of the peak/bottom detection circuit 200.

The peak/bottom detection circuit 200 of the first embodiment detectsthe peak value of the power voltage output from the power source 201 ina case in which the peak detection mode is selected by the MODE signal,and detects the bottom value of the power voltage output from the powersource 201 in a case in which the bottom detection mode is selected bythe MODE signal.

The control signals SWn_P, SWn_D, and SWn_H are generated based on theSTB signal and the CMPO signal output from the comparator 205. Each ofthe switches SW1, SW2, and SW3 of the first embodiment switches theconnection destination (the terminal P, the terminal D, and the terminalH) of the terminal C in response to the control signals SWn_P, SWn_D,and SWn_H.

The A/D conversion section 300 of the first embodiment corresponds to anA/D converter having lower power, and converts a voltage, which isindicated by the DETO signal output from the calculation amplifier 206,into a digital value.

Next, referring to FIG. 2, the switches SW1, SW2, and SW3 of the firstembodiment will be described. FIG. 2A and FIG. 2B are diagrams forexplaining the switches SW1, SW2, and SW3 of the first embodiment. FIG.2A is a diagram illustrating the switches SW1, SW2, and SW3, and FIG. 2Billustrates a truth table.

As illustrated in FIG. 2A, the switches SWn of the first embodimentdetermine the connection destination of the terminal C as one of theterminal P, the terminal D, and the terminal H, depending on respectivevalues of the control signals SWn_P, SWn_D, and SWn_H. Relationshipsbetween respective values of the control signals SWn_P, SWn_D, and SWn_Hand the connection destination in the switch SWn are indicated in atruth table 21 in FIG. 2B. A relationship that is not indicated in thetruth table 21 is not defined.

In the switches SWn of the first embodiment, the terminal C is connectedto the terminal P in a case in which a value of the control signal SWn_Pis a high level (hereinafter, called “H level”), a value of the controlsignal SWn_D is a low level (hereinafter, called “L level”), and a valueof the control signal SWn_H is the L level. That is, the capacitor Cn isconnected to the power source 201, and is charged (pre-charged) by thevoltage supplied from the power source 201.

Moreover, in the switch SWn, the terminal C is connected to the terminalD in a case in which the value of the control signal SWn_P is the Llevel, the value of the control signal SWn_D is the H level, and thevalue of the control signal SWn_H is the L level. That is, the capacitorCn is connected to the inverting terminal of the comparator 205. In thepeak/bottom detection circuit 200, in response to connecting thecapacitor Cn to the comparator 205, the power voltage and the voltage ofthe capacitor Cn are compared, and the peak value or the bottom value ofthe power voltage is detected.

Moreover, in the switch SWn, the terminal C is connected to the terminalH in a case in which the value of the control signal SWn_P is the Llevel, the value of the control signal SWn_D is the L level, and thevalue of the control signal SWn_H is the H level. That is, the capacitorCn is connected to one input terminal of the calculation amplifier 206,and the DETO signal depending on the voltage of the capacitor Cn isoutput from the calculation amplifier 206 to the A/D conversion section300.

As described above, in the peak/bottom detection circuit 200, the switchSWn is switched in accordance with the control signals SWn_P, SWn_D, andSWn_H, whereby three states are defined with respect to the capacitorsCn (n=1, 2, and 3), respectively.

The three states correspond to a state of pre-charging the capacitor Cn,a state (of setting) until the peak value or the bottom value of thepower voltage is detected from bringing the voltage of the capacitor Cnclose to the power voltage, and a state (hold state) for maintaining avoltage value of the capacitor Cn in order for the A/D conversionsection 300 to conduct the sampling. In the following, the state ofpre-charging the capacitor Cn is called “pre-charge state”, the state ofdetecting the peak value or the bottom value is called “detectionstate”, and the state of maintaining the voltage value of the capacitorCn is called “hold state”.

In the peak/bottom detection circuit 200 of the first embodiment, threeor more capacitors Cn and three or more switches SWn are provided, andstates of the capacitors Cn are subsequently changed so that the statesof the capacitors Cn are different from each other.

In the first embodiment, as described above, by switching the states ofthe capacitors Cn so that the states of the capacitors Cn are differentfrom each other, and one of the capacitors Cn becomes a capacitor in thedetection state.

By this configuration, according to the first embodiment, the detectionstate is not discontinued, and the occurrence of dead time iscontrolled. Therefore, according to the first embodiment, it is possibleto successively output a detection result of the peak value or thebottom value.

Next, referring to FIG. 3A and FIG. 3B, a switch between the peakdetection mode and the bottom detection mode by the controller 210 willbe described.

FIG. 3A and FIG. 3B are diagrams for explaining the switch between thepeak detection mode and the bottom detection mode. FIG. 3A is a diagramfor explaining the mode switching section 220 including the controller210. FIG. 3B is a diagram for explaining values of the control signalSWP and the control signal SWB in each mode.

The mode switching section 220 of the first embodiment inputs the CMPOsignal and the MODE signal, and outputs the control signal SWP and thecontrol signal SWB. The control signal SWP is supplied to the switchSW4, and the control signal SWB is supplied to the switch SW5.

The mode switching section 220 of the first embodiment includes a NOTcircuit 221, and AND circuits 222 and 223.

The CMPO signal is supplied to one input terminal of the AND circuit 222and one input terminal of the AND circuit 223. The MODE signal issupplied to the other input terminal of the AND circuit 222 and an inputterminal of the NOT circuit 221.

An output of the NOT circuit 221 is supplied to the other input terminalof the AND circuit 223. An output of the AND circuit 223 is supplied asthe control signal SWB to the switch SW5.

In the first embodiment, as indicated by the truth table 31 in FIG. 3B,in a case in which the values of the MODE signal and the CMPO signal arethe L level, the control signal SWP and the control signal SWB becomethe L level.

Also, as indicated in the truth table 31, in a case in which the MODEsignal indicates the L level and the CMPO signal indicates the H level,the control signal SWP becomes the L level and the control signal SWBbecomes the H level.

That is, in the first embodiment, in a case in which the value of theMODE signal is the L level, the control signal SWP maintains the Llevel, and, the switch SW4 becomes in a disconnection state. In otherwords, the peak/bottom detection circuit 200 discharges the voltage ofthe capacitor Cn and operates as the bottom detection mode for detectingthe bottom value of the power voltage of the power source 201, when thevalue of the MODE signal is the L level.

Also, as indicated in the truth table 31, in a case in which the MODEsignal indicates the H level and the value of the CMPO signal is the Llevel, both the control signal SWP and the control signal SWB become theL levels. Moreover, in a case in which the values of the MODE signal andthe CMPO signal are the H level, the control signal SWP becomes the Hlevel and the control signal SWB becomes the L level.

That is, in the first embodiment, in a case in which the value of theMODE signal is the H level, the control signal SWB maintains the L leveland, the switch SW5 becomes in the disconnection state. In other words,when the value of the MODE signal is the H level, the peak/bottomdetection circuit 200 charges the capacitor Cn by the power source 202,and operates as the peak detection mode for detecting the peak value ofthe power voltage of the power source 201.

Next, an operation of the peak/bottom detection circuit 200 will bedescribed with reference to FIG. 4 and FIG. 5.

FIG. 4 is a timing chart for explaining the operation of the peak/bottomdetection circuit in the peak detection mode.

First, the operation of the peak/bottom detection circuit 200 in asection K1 from a timing T1 to a timing T2 will be described. Thesection K1 corresponds to one period of the STB signal. In other words,the timings Tn (n=1, 2, . . . ) in FIG. 4 are timings synchronizingrises of the STB signal. Accordingly, in the first embodiment, in thepeak/bottom detection circuit 200, a period when the capacitor Cn is inthe pre-charge state, a period when the capacitor Cn is in the detectionstate, and a period when the capacitor Cn is in the hold statecorrespond to one cycle of the STB signal, and time ratios are the same.

In an example in FIG. 4, at the timing T1, the value of the controlsignal SW1_P is the H level, and the values of the control signal SW1_Dand the control signal SW1_H are the L level. Accordingly, in thesection K1, the capacitor C1 becomes in the pre-charge state in whichthe capacitor C1 is connected to the power source 201 through the switchSW1, and a voltage VC1 increases.

Moreover, at the timing T1, the values of the control signal SW2_P andthe control signal SW2_D are the L level, and the value of the controlsignal SW2_H is the H level. Accordingly, in the section K1, thecapacitor C2 becomes in the hold state in which the capacitor C2 isconnected to the calculation amplifier 206 through the switch SW2. Inthe section K1, the calculation amplifier 206 outputs the DETO signaldepending on a voltage VC2 of the capacitor C2 to the A/D conversionsection 300.

Moreover, at the timing T1, the values of the control signals SW3_P andthe control signal SW3_H are the L level, and the value of the controlsignal SW3_D is the H level. Accordingly, in the section K1, thecapacitor C3 becomes in the detection state in which the capacitor C3 isconnected to the comparator 205 through the switch SW3. At this time,the capacitor C3 is charged by the current source 203 in order for avoltage VC3 to follow a power voltage VDD.

Next, a section K2 from the timing T2 to a timing T3 will be described.In the first embodiment, the controller 210 synchronizes with a rise ofthe STB signal, switches the values of the control signal SWn_P, thecontrol signal SWn_D, and the control signal SWn_H, and subsequentlyswitches the states of the capacitors C1 to C3 to be different from eachother.

At the timing T2, the values of the control signal SW1_P and the controlsignal SW1_H are the L level, and the value of the control signal SW1_Dis the H level. Accordingly, in the section K1, the capacitor C1 becomesin the detection state in which the capacitor C1 is connected to thecomparator 205 through the switch SW1.

Also, at the timing T2, the value of the control signal SW2_P is the Hlevel, and the values of the control signal SW2_D and the control signalSW2_H are the L level. Accordingly, in the section K2, the capacitor C2becomes in the pre-charge state in which the capacitor C2 is connectedto the power source 201 through the switch SW2.

Also, at the timing T2, the values of the control signal SW3_P and thecontrol signal SW3_D are the L level, and the value of the controlsignal SW3_H becomes the H level. Accordingly, in a section K3, thecapacitor C3 becomes in the hold state in which the capacitor C3 isconnected to the calculation amplifier 206 through the switch SW3.

Referring to FIG. 4, at a timing Tp in the section K2, the peak value ofthe power voltage VDD is detected. The peak value is a value of thepower voltage VDD where the voltage of the capacitor Cn applied to theinverting input terminal of the comparator 205 becomes higher than thepower voltage VDD.

At the timing Tp, when the peak value is detected, the CMPO signal asthe output signal of the comparator 205 becomes the L level.

Moreover, in the section K2, when the peak value is detected, thevoltage VC1 of the capacitor C1 is maintained. At the timing T3, whenthe terminal C of the switch SW1 is connected to the terminal H and thecapacitor C1 becomes in the hold state, the DETO signal depending on thevoltage VC1 is output from the calculation amplifier 206, and issupplied to the A/D conversion section 300.

Moreover, at the timing T3, the connection destination of the terminal Cof the switch SW2 is switched from the terminal P to the terminal D, andthe capacitor C2 becomes in the detection state from the pre-chargestate.

Also, at the timing T3, the connection destination of the terminal C ofthe switch SW3 is switched from the terminal H to the terminal P, andthe state of the capacitor C3 is changed from the hold state to thepre-charge state whereby the voltage of the capacitor C3 follows thepower voltage VDD.

By this operation, according to the first embodiment, it is possible toreduce power consumption for charging the capacitor Cn to follow thepower voltage after the capacitor Cn is discharged. Also, according tothe first embodiment, it is possible to reduce occurrences of noise dueto an inrush charging current, which occurs during charging of thecapacitor Cn after the voltage VCn of the capacitor Cn is reset.

Furthermore, in the first embodiment, by setting the capacitor Cn in thehold state for one period of the STB signal, it is possible to providesufficient time for the A/D conversion section 300 to sample the voltagevalue of one of the capacitors Cn.

Next, an operation of the peak/bottom detection circuit 200 in thebottom detection mode will be described with reference to FIG. 5.

FIG. 5 is a timing chart for explaining the operation of the peak/bottomdetection circuit in the bottom detection mode.

In FIG. 5, an example is depicted, in which the bottom value is detectedat a timing Tb in the section K3 from the timing T3 to a timing T4.

The operations of the switches SW1 to SW3 are the same as FIG. 4.Referring to FIG. 5, in a case of the bottom detection mode, when thevalue of the power voltage VDD is greater than the voltage VCn of thecapacitor Cn in the detection state, the CMPO signal is output. When thevalue of the power voltage VDD becomes lower than the voltage VCn of thecapacitor Cn in the detection state, the value of the power voltage VDDis detected as the bottom value. Operations other than that describedabove are the same as those described in FIG. 4, and the explanationthereof will be omitted.

In the following, the comparator 205 and the calculation amplifier 206will be described in reference to FIG. 6A, FIG. 6B, and FIG. 7.

FIG. 6A and FIG. 6B are diagrams for explaining an example of thecomparator. The comparator 205 of the first embodiment is a clockedcomparator. FIG. 6A illustrates an example of the comparator 205 at areset operation, and FIG. 6B illustrates an example of the comparator205 at a comparing operation.

The comparator 205 includes a P-channel transistor P1 and a P-channeltransistor P2. The P-channel transistor P1 inputs an input signal IN1 toa gate, and supplies a current I1 to an output terminal OUT1. TheP-channel transistor P2 inputs an input signal IN2, which is adetermination value or a comparison result, to the gate, and supplies acurrent I2 to an output terminal OUT2. Sources of these transistors P1and P2 are connected to a power source Vcc. The comparator 205 furtherincludes an amplifier circuit that amplifies a voltage potentialdifference between the output terminals OUT1 and OUT2 based on thevoltage potential difference between the output terminal OUT1 and theoutput terminal OUT2.

This amplifier circuit includes P-channel transistors P3 and P4 whosegates and drains are cross-connected, and N-channel transistors N5 andN6 whose gates and drains are cross-connected; thus, this currentincludes a latch function.

Also, the comparator 205 includes a pair of switches SW61 and SW62 thatturn ON at the reset operation and cause the output terminals OUT1 andOUT2 to be a ground voltage. The switches SW61 and SW62 are in an ONstate at the reset operation depicted in FIG. 6A, and the switches SW61and SW62 are in an OFF state at the comparison operation depicted inFIG. 6B.

FIG. 7 is a diagram illustrating an example of the calculationamplifier. The calculation amplifier 206 includes transistors TR1through TR9 and an inverter 71. The Transistors TR1, TR2, TR5, and TR9are N-channel transistors, and the transistors TR3, TR4, TR6, TR7, andTR8 are P-channel transistors.

An inverted phase input is applied to a gate of the transistor TR1, anda positive phase input is applied to a gate of the transistor TR2. Apower down signal PD, which is inverted by the inverter 71, is appliedto the transistor TR8. The power down signal PD is applied to thetransistor TR9.

In the calculation amplifier 206, when the power down signal PD becomeactive, the transistor TR8 and the transistor TR9 are turned on, and thetransistor TR5 and TR6 and the transistor TR7 are turned off. Anoperation of the calculation amplifier 206 stops, and an output OUTbecomes in a hi-impedance state.

The comparator 205 in FIG. 6A and FIG. 6B, and the calculation amplifier206 in FIG. 7 are examples; thus, configurations of the comparator 205and the calculation amplifier 206 in the first embodiment are notlimited to the above described examples.

As described above, according to the first embodiment, by includingthree capacitors C1, C2, and C3 and subsequently switching the state ofeach of capacitors C1 to C3, it is possible to successively detect thepeak value or the bottom value of the power voltage, and to reduce deadtime.

Second Embodiment

A second embodiment will be described with reference to drawings. In thesecond embodiment, differently from the first embodiment, four or morecapacitors Cn are provided. Hence, in the following, different portionsfrom the first embodiment will be described, the same reference numeralsas those used in the first embodiment are assigned to components havingthe same functional configuration as those of the first embodiment, andexplanations thereof are omitted.

FIG. 8 is a diagram illustrating an A/D converter in the secondembodiment. An A/D converter 100A of the second embodiment includes apeak/bottom detection circuit 200A, and an A/D conversion section 300.

The peak/bottom detection circuit 200A of the second embodiment includesa controller 210A, the power sources 201 and 202, the current sources203 and 204, the comparator 205, the calculation amplifier 206, theswitches SW1 through SW5, a switch SW41, a switch SW51, and capacitorsC1 through C5.

The controller 210A of the second embodiment outputs the control signalsSWn_P, SWn_D, and SWn_H to define which of the terminal P, the terminalD, and terminal H is to be the connection destination of the terminal Cfor each of the switches SW1 through SW3, SW41, and SW51.

In the second embodiment, by providing five capacitors Cn with respectto three states: the pre-charge state, the detection state, and the holdstate, it is possible to change the time ratios of a time of thepre-charge state, a time of the detection state, and a time of the holdstate in the peak/bottom detection circuit 200A.

In an example in FIG. 8, among the capacitor C1 to the capacitor C5, thecapacitors C1, C2, and C3 simultaneously become in the pre-charge state.In this state, a time when the capacitors C1 to C3 are in the pre-chargestate corresponds to a time for one cycle of the STB signal. That is, inthe second embodiment, three capacitors Cn exist to be pre-charged forthe time of one cycle of the STB signal. This is equivalent to placingone capacitor Cn in the pre-charge state for a time of three cycles ofthe STB signal.

As described above, in the second embodiment, by simultaneously settinga plurality of capacitors Cn to be the same state, it is possible tochange the time ratios of the time of the pre-charge state, the time ofthe detection state, and the time of the hold state.

In FIG. 8, the capacitors C1 to C3 are simultaneously set to be in thepre-charge state; however, this operation is not limited to thisexample. For instance, in the second embodiment, the capacitors C1 andC2 may be simultaneously set to be in the pre-charge state, and thecapacitors C3 and C4 may be simultaneously set to be in the detectionstate.

In the second embodiment, as described above, it is possible to changethe time ratio for each of the pre-charge state, the detection state,and the hold state. Hence, for instance, if the second embodiment isapplied to a case of setting a time of the pre-charge or a settling timeto be longer than a time for the A/D conversion section 300 to samplethe voltage values of the capacitors Cn, it is possible to employ theA/D conversion section 300 more effectively.

Third Embodiment

In the following, a third embodiment will be described with reference todrawings. In the third embodiment, differently from the firstembodiment, a plurality of the peak/bottom detection circuits describedin the first embodiment are mounted in an integrated circuit. Hence, inthe following, different portions from the first embodiment will bedescribed, the same reference numerals as those used in the firstembodiment are assigned to components having the same functionalconfiguration as those of the first embodiment, and explanations thereofare omitted.

FIG. 9 is a first diagram illustrating an example of an integrateddevice of the third embodiment. The integrated circuit 400 of the thirdembodiment includes a plurality of peak/bottom detection circuitsincluding at least a peak/bottom detection circuit 200B-1 and apeak/bottom detection circuit 200B-2, the A/D conversion section 300,and a switch circuit 350.

In the third embodiment, different from the peak/bottom detectioncircuit 200 of the first embodiment, a plurality of the peak/bottomdetection circuits 200B, which are the peak/bottom detection circuit200B-1 and the peak/bottom detection circuit 200B-2, share the powersource 201.

Also, in the integrated circuit 400 of the third embodiment, the switchcircuit 350 includes switches SW31 and SW32. The switch SW31 switches aconnection and a disconnection between the peak/bottom detection circuit200B-1 and the A/D conversion section 300. The switch SW32 switches aconnection and a disconnection between the peak/bottom detection circuit200B-2 and the A/D conversion section 300.

The switch circuit 350 may control ON or OFF of the switch SW31 and theswitch SW32 by a switch control signal input from a high-level circuit(not shown) of the integrated circuit 400. For instance, by the switchcircuit 350 alternately turning on the switch SW31 and the switch SW 32,it is possible to convert voltages, which are output from both thepeak/bottom detection circuit 200B-1 and the peak/bottom detectioncircuit 200B-2, into digital values.

FIG. 10 is a second diagram illustrating the example of the integrateddevice of the third embodiment. An integrated circuit 400A depicted inFIG. 10 includes peak/bottom detection circuits 200-1 through 200-4, andthe A/D conversion section 300, and the switch circuit 360.

In the integrated circuit 400A, the switch circuit 360 includes switchesSW33, SW34, SW35, and SW36.

The switch SW33 switches a connection and a disconnection between thepeak/bottom detection circuit 200-1 and the A/D conversion section 300,and the switch SW34 switches a connection and a disconnection betweenthe peak/bottom detection circuit 200-2 and the A/D conversion section300. Moreover, the switch SW35 switches a connection and a disconnectionbetween the peak/bottom detection circuit 200-3 and the A/D conversionsection 300, and the switch SW36 switches a connection and adisconnection between the peak/bottom detection circuit 200-4 and theA/D conversion section 300.

A switch control signal may be supplied to instruct switching of theswitches SW33 to SW36 from a high-level circuit (not shown) of theintegrated circuit 400A, and the switch circuit 360 may sequentiallyswitch the switches SW33 to SW36 in response to this switch controlsignal.

Moreover, in the integrated circuit 400A, from this high-level circuit,an output instruction signal for instructing to output the DETO signalmay be supplied with respect to the peak/bottom detection circuits 200-1to 200-4.

In this case, the switch control signal supplied to the switch circuit360 and the output instruction signal supplied to the peak/bottomdetection circuits 200-1 to 200-4 are synchronized signals.Specifically, for instance, in a case in which the switch SW33 is turnedon and the peak/bottom detection circuit 200-1 and the A/D conversionsection 300 are connected, the output instruction signal of the DETOsignal may be supplied to the peak/bottom detection circuit 200-1.

In the example depicted in FIG. 10, four peak/bottom detection circuits200 are mounted in the integrated circuit 400A; however, a configurationis not limited to this example. Any number of the peak/bottom detectioncircuits 200 may be mounted in the integrated circuit 400A.

FIG. 11 is a diagram illustrating an example of an arrangement of thepeak/bottom detection circuits in the integrated circuit. In FIG. 11,the example of the arrangement of the peak/bottom detection circuits200-1 to 200-4 in the integrated circuit 400A is depicted.

In the integrated circuit 400A, for instance, the peak/bottom detectioncircuits 200-1 to 200-4 may be deployed at four corners of theintegrated circuit 400A, respectively. In other words, the peak/bottomdetection circuits 200-1 to 200-4 may be deployed in vicinities of edgesof a substrate of the integrated circuit 400A.

In the third embodiment, by deploying the peak/bottom detection circuits200-1 to 200-4 as described above, for instance, it is possible todetect the peak value or the bottom value of the power voltage atdifferent positions with respect to a power source line formed on thesubstrate.

In this case, for instance, it is preferable that each of thepeak/bottom detection circuits 200 is deployed in a vicinity or the likeof a circuit having a greater power consumption, from among circuitsexecuted by the integrated circuit 400A. Also, in a case of detectingthe power voltage at different positions on the power source line, it ispreferable that the peak/bottom detection circuits 200 are distributedand arranged on the substrate of the integration circuit 400A.

According to the first embodiment to the third embodiment, it ispossible to suppress occurrences of dead time.

Although the present invention has been described based on therespective embodiments, the present invention is not limited torequirements described in the above embodiments. Regarding these points,it is possible to change the scope of the present invention within thescope not to obscure it, and requirements can be appropriatelydetermined according to an application form.

What is claimed is:
 1. A peak/bottom detection circuit, comprising:three or more capacitors; a comparator configured to compare a voltageof one of the three or more capacitors with an input voltage; acalculation amplifier configured to amplify a voltage of one of thethree or more capacitors; three or more switches respectivelycorresponding to the three or more capacitors, each of the three or moreswitches configured to connect a corresponding capacitor among the threeor more capacitors to one of the comparator, the calculation amplifier,and a source of the input voltage; and a controller configured togenerate control signals for sequentially switching connectiondestinations of the three or more capacitors and to supply the controlsignals to the three or more switches, respectively, in which theconnection destinations of three capacitors among the three or morecapacitors are different from each other.
 2. The peak/bottom detectioncircuit as claimed in claim 1, wherein the controller generates thecontrol signals based on an output signal of the comparator, which isinput to the controller, and a timing signal for reading a voltage of acapacitor connected to the calculation amplifier among the three or morecapacitors.
 3. The peak/bottom detection circuit as claimed in claim 1,wherein a number of the three or more capacitors is four or more, anumber of the three or more switches is four or more; and wherein thecontroller generates the control signals for the connection destinationsof at least two capacitors to be the same among four or more capacitors.4. The peak/bottom detection circuit as claimed in claim 1, wherein foreach of the three or more capacitors, a connection destination isswitched in an order of the source of the input voltage, the comparator,and the calculation amplifier; and the connection destination is nextswitched to the source of the input voltage from the calculationamplifier.
 5. An analog to digital converter, comprising: a peak/bottomdetection circuit; and an analog to digital conversion section, whereinthe peak/bottom detection circuit includes three or more capacitors; acomparator configured to compare a voltage of one of the three or morecapacitors with an input voltage; a calculation amplifier configured toamplify a voltage of one of the three or more capacitors; three or moreswitches respectively corresponding to the three or more capacitors,each of the three or more switches configured to connect a correspondingcapacitor among the three or more capacitors to one of the comparator,the calculation amplifier, and a source of the input voltage; and acontroller configured to generate control signals for sequentiallyswitching connection destinations of the three or more capacitors and tosupply the control signals to the three or more switches, respectively,in which the connection destinations of three capacitors among the threeor more capacitors are different from each other, wherein the analog todigital conversion section is connected to a latter stage of thecalculation amplifier.
 6. An integrated circuit, comprising: a pluralityof peak/bottom detection circuits; an analog to digital sectionconnected to a latter stage of the plurality of peak/bottom detectioncircuits; and a switch circuit, wherein each of the plurality ofpeak/bottom detection circuits includes three or more capacitors; acomparator configured to compare a voltage of one of the three or morecapacitors with an input voltage; a calculation amplifier configured toamplify a voltage of one of the three or more capacitors; three or moreswitches respectively corresponding to the three or more capacitors,each of the three or more switches configured to connect a correspondingcapacitor among the three or more capacitors to one of the comparator,the calculation amplifier, and a source of the input voltage; and acontroller configured to generate control signals for sequentiallyswitching connection destinations of the three or more capacitors and tosupply the control signals to the three or more switches, respectively,in which the connection destinations of three capacitors among the threeor more capacitors are different from each other.
 7. The integratedcircuit as claimed in claim 6, wherein the three or more peak/bottomdetection circuits are deployed in vicinities of edges of a substrate ofthe integrated circuit, respectively.